


Coveting Innocence

by MeGaLoTrash



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell, Dry Humping, Ecto-Penis (Undertale), Ecto-Vagina (Undertale), M/M, Mapleblossom - Freeform, Marking, Masturbation, Multiple Orgasms, Obsessive Behavior, Olfaction, Omorashi, Oral Sex, Overstimulation, Possessive Behavior, Sexual Coercion, Stealing clothing, Watersports, dubcon, extra-virgin Papyrus, innocence kink, papcest - Freeform
Language: English
Status: Completed
Published: 2018-03-03
Updated: 2018-03-03
Packaged: 2019-03-26 13:23:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,208
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13858644
Author URL: https://archiveofourown.org/users/MeGaLoTrash/pseuds/MeGaLoTrash
Summary: Papyrus is innocent, pure, sweet and perfect- everything Slim isn't. So hehasto have him.





	Coveting Innocence

**Author's Note:**

  * For [Silver_Centurion](https://archiveofourown.org/users/Silver_Centurion/gifts).



> Please mind the tags! Particularity the *dubcon* warning.

When his brother had bitched at him to visit some of their alternate universes, Slim had originally protested. He’d only mentioned fixing the machine in their shed casually when giving his daily report, he had no idea Black would have pressed him for details so eagerly. He guessed that his brother wanted to check out his competition, to see if he was the ‘best’ sans or some other bullshit. Slim could have cared less, but then they came across a universe that was so fucking vanilla that he stuck out like a sore thumb. Rather than feel uncomfortable, Slim enjoyed the looks of disgust and terror that his mere presence would provoke.

Slim was about to suggest that he and Black had some ‘fun’ with the locals...but then he had met Papyrus.

While the Sans of this universe and Black squared each other up, Slim had to deal with Papyrus running up to him and pulling him into a hug. Apparently the brothers were used to getting visitors from lots of different universes, so their appearance did little to sway his cheerful demeanour. Papyrus had been quick to lead him into their house, giving Slim a tour while asking questions about his universe and if he and his brother had any nicknames they could use. Hearing Papyrus saying his name as he linked their arms together made Slim’s shrivelled up soul flutter in his ribcage. He'd never met anyone so trusting and open with affection, yet so endearingly clueless at the same time. He knew from that moment onwards that he had to have this sweet angel for himself, no matter what it was going to take 

Slim was completely smitten; he couldn’t believe that this pure being was actually a version of himself. And he could hardly wait for the opportunity to completely ruin him. Over the next month he made frequent trips to Papyrus’s universe to spend time with him, even though both of their brothers disapproved. Sans hadn’t quite seen through his friendly act, but Slim could tell that the guy was unsettled by the amount of time he was spending with Papyrus. Black on the other hand couldn’t care less about who he was trying to fuck, but he was disgusted with the way Slim behaved like a pushover around his newfound obsession. _trust black to completely miss the bigger picture_. If he had even the slightest bit of patience he would see that tactics from their universe just wouldn’t work with such a delicate flower. Bedding Papyrus may take a little more effort than he was used too, but just thinking about the pay off made him instantly hard. 

But his sweet Pappy didn’t take any notice of anyone’s attempts to split them apart, in fact he was quick to tell both of their brothers to stop being so nosey. According to Papyrus, Slim was apparently his ‘new special friend’ and both of them needed to mind their own business. Papyrus had not only defended him unnecessarily, but he had called him a _special_ friend. Slim couldn’t wipe the shit-eating grin off his face that night if he tried. And with their brothers slinking away after being berated, Slim found the opportunity to slip into Papyrus’s room unnoticed when he was cooking. He was only there for a minute, but he managed to find what he was looking for straight away sitting on the top of Papyrus’s laundry basket. 

When Slim returned to his universe that night he pretended to go out on patrol like Black had ordered, only to teleport back into his bedroom as soon as he was out of sight. He bolted his door quickly, pulling the panties he’d stolen earlier out of his pocket and immediately bringing them to his face. He knew his perfect Papyrus was squeaky clean, but there was a faint but heavenly scent left behind on the white cotton. There was no mistaking it; his soon to be lover preferred to summon a pussy with his magic, just like he had suspected. Slim took in a deep breath, muffling a moan with the panties as he lost himself. He sat back on his bed, unbuckling his pants so that he could free the magic that was starting to form into a cock before freezing. 

He had a _much_ better idea. 

Shuffling onto his bed and fully removing his pants he tried to refocus his magic into something else, something like what he imagined Papyrus would form. They were the same person after all, so Papyrus’s magic must have felt a little like his own. He teased his outer lips with a hiss, screwing his sockets shut as he ran his fingers over the soft magic of his entrance. There was something so delightfully perverse in pleasuring himself while he imagined sticking his fingers into Papyrus’s cunt instead. He stuck out his tongue and began to suckle on the fabric, making himself cum over and over as he imagined tasting his angel from the source. 

Since that night Slim’s patience had started to waver. He had started introducing more contact with Papyrus when they were alone; hugs that lasted a little longer each time, a kiss on his forehead, and a few lingering touches. That coupled with the way Slim would praise Papyrus as often as possible had earned him more than a few starry eyed looks of wonder. And each time he would fall just a little further. Slim wanted to savour the moments, really enjoy the build up, but his fantasies were becoming so intense when he was with Papyrus. Slim knew there was an increasing risk of him losing focus and slipping up, ruining all the work he’d been doing building up the ‘trust’ between them. The one thing that was working in his favour though was how Papyrus was even more clueless than he had originally anticipated. Slim realised that his best chance at success would be working Papyrus up, while keeping him as oblivious as possible, until he was turned on enough to respond purely on instinct. 

It may have been a little sooner than he had planned, but Slim decided that he was going to try going in for the kill at the next available opportunity. The problem was finding a time when they were completely alone, without the risk of anyone interrupting them if his sweet boy became loud. And Slim just _knew_ he would be; Papyrus would start of shy and embarrassed before Slim turned him into a screamer. He shuddered just thinking about that duality; caught between being shy and turning into his whore.

It took another two excruciating weeks of waiting around before Slim finally got his chance. They were hanging out in Papyrus’s living room, watching some drivel from this universes entertainment robot while working their way through a bowl popcorn and a few sodas. Sans had been hanging about in the nearby chair, pretending to watch the show while stealing looks in Slim’s direction 

Slim had resigned himself to nothing more than enjoying Papyrus’s company when suddenly the asshole’s phone had started ringing. Sans spoke in hushed tones but it was clear that whoever was calling needed his urgent attention. When he hung up he had mumbled something about being summoned by the king and needing to leave, but Slim hadn’t been listening. For all he knew there was an emergency with the king’s beard needing braiding or some shit. It didn’t matter. This was the opportunity he’d been waiting for; long, uninterrupted time with Papyrus. With his brother on the opposite side of the underground. He had to hide his grin behind his hand as excited magic warmed his bones. His overwhelming sense of anticipation was making it hard to keep still but he refused to mess this up. Not now he was so close to getting what he wanted. 

Sans gathered his things quickly and waved goodbye to Papyrus while heading out the door. He hesitated just as he was leaving, stealing a glance back in the direction of the couch. Slim could see the inner turmoil of leaving Papyrus alone with him written clearly across Sans’s features. He played dumb while grabbing another handful of popcorn, but inside he was overflowing with smugness. Sans had every right to be worried considering what Slim planned to do, but he had given the other skeleton no reason to be able to voice his concerns. The sound of the door closing and Sans locking them in was a sweet victory in its own right. But now that they were alone the real fun could start.

Slim waited a few minutes just to make sure Sans was gone for good before putting his plan into action. He stood up to stretch his bones, glancing sideways at Papyrus as his sweater rode up and exposed the top of his pelvic bone. Papyrus’s naive nature meant that he looked in Slim’s direction straight away, but his cheekbones was peppered with the lightest blush upon seeing the exposed bone before he looked away in embarrassment. It was so fucking cute of a reaction that Slim found urges to pounce on Papyrus and take exactly what he wanted harder than ever to ignore. But this was all part of his plan, and taking Papyrus would be so much more rewarding if his double was at least somewhat compliant. 

He sat back down and pat his lap in an invitation for Papyrus to sit there. They had done this a few times when reading a book, so it was no surprise when Papyrus moved on top of him without hesitation. It was the first thing Slim had worked on getting Papyrus used too when he had devised his plan, and the fact he was already relaxing into the embrace just made crossing the next line easier. He let Papyrus adjust himself and get comfortable, staring at the screen over his shoulder even though all of his attention was focused on the press of his body against him. Slim had no idea how his hard and coarse bones in a different universe could feel so smooth, but yet here Papyrus was. A skeleton so pure and innocent he had no idea what Slim’s true intentions were. 

But that was about to change.

Slim made sure to move things forward at an incredibly slow pace to start. He wanted to push the boundaries so subtly that Papyrus wouldn’t realise until he felt too good to stop. Slim relaxed a little, letting the magic he’d been holding back form slowly into his long cock. He was already half hard but he willed himself to stay calm and let Papyrus get used to feeling him under his own pelvis. If Papyrus noticed anything had changed he didn’t show it, his eyes were still fixed on the t.v. screen as he sipped a fresh can of soda. It felt incredible to know that there was only a few layers of material separating his cock and Papyrus’s bare pelvis, but he knew it would feel even better if he could coax the other skeleton’s magic to form. 

Slim bumped his hips up a fraction and had to hold back from hissing between his teeth. Papyrus shifted a little this time, unintentionally bumping his tail-bone against the cock beneath him. Slim could feel himself slowly getting harder, only this time he didn’t try and stop himself. Papyrus might have only been squirming to adjust himself subconsciously, but that just meant that on some level Papyrus could feel his cock pressing into him. Slim moved again, only this time with a little more purpose, rolling his hips upwards so that Papyrus would be able to feel him properly. It seemed like a huge line to cross when in reality the movement was small enough that Papyrus would only register how nice it felt. Slim could only imagine what was going through Papyrus’s head as he snuggled into him further, he wondered if his angel had even noticed his magic was reacting to the stimulation. 

It was such a subtle smell, but considering Slim had had his face buried into Papyrus’s panties until all trace of the sweet skeleton had disappeared. There was not a doubt in his mind that he wasn’t just pressing against bone any more. And the fucking _noises_. It was obvious that Papyrus hadn’t even noticed with his attention still on the show; but his breathing was heavier, and every now and again he’d let slip an almost inaudible whimper. Slim could feel drool dripping down his mandible, having to swipe his tongue across his teeth to stop it reaching Papyrus’s scarf. He really wanted to lean forward and drag his tongue across Papyrus’s bones, but it comforted him to know that he would be able to _very_ soon. 

Within next few minutes Slim went from hardly moving at all to a slow rhythm of rolling his hips upwards. Slim could hardly believe he was actually doing this, that he had managed to build their relationship up so that he could dry hump his double on the couch. He was able to feel the outline of Papyrus’s pussy through his shorts as the material became wet and clung to his outer lips. Slim wasn’t sure when exactly Papyrus had realised there was something going on, but his sweet angel had done nothing to try and stop him yet. It was just like he had planned. Slim knew Papyrus was too polite, to afraid to hurt his feelings, to actually say or do anything that might offend him. It was only a matter of time before it became too much for Papyrus to ignore though, Slim needed to make sure that he started to really enjoy himself. So that his body wouldn’t even want to pull away, not when Slim could give him pleasure he’d never experienced before. 

Slim tentatively rested a hand on the top of Papyrus’s pelvic bone as he shifted them both slightly. In the new position he was able to drag his now rock hard cock across Papyrus’s folds fully, making sure to put the most force into the end of his thrusts so that the head of his cock would bump against Papyrus’s clit. That made his sweet double gasp, before moving his hips backwards so that he could feel it again. This caught Slim off guard completely. He groaned in pleasure and effectively shattered the silence between them.

“O-Oh I’m So Sorry Slim, I-I’ll Just Move If I’m H-hurting You” Papyrus blabbered quickly, before trying to move on trembling legs.

This was it. The make or break moment that would determine whether all of this build up had been worth it. 

Slim wrapped both of his arms around Papyrus, pulling him close. “but i _really_ want you to stay, little pappy” he purred before thrusting properly, giving Papyrus a taste of what it could really feel like. “doesn’t that feel _so_ good?”

Papyrus didn’t answer, but he didn’t need too. He used his new leverage to set up a fast rhythm, not needing to see Papyrus for him to know his expression was one of pleasure. Slim could hear it in the way his sweet noises had progressed into confused whines. Slim let himself go a little, humping Papyrus fully as he nipped and licked his smooth vertebrae The change in Papyrus happened suddenly, when Slim starting sliding against his hot cunt _just right_ , but it would forever be seared into his mind. There was a series of gasps, short and quick moans rocketing into a crescendo, and Papyrus’s body locking up completely. 

With the way Papyrus reacted, Slim wouldn’t have been surprised if that was his first orgasm ever. 

Slim didn’t give Papyrus any chance to recover, pushing him upwards and turning him around so he could tear away his the clothing on his bottom half. Slim buried his face into Papyrus’s dripping mound, inhaling deeply as he pushed his tongue inside. Papyrus was unable to control his noises this time as his over-sensitive magic was explored, grasping at Slim’s shoulders for support. Slim could feel himself going crazy, the feeling of Papyrus overwhelming his senses being better than he could have ever imagined. While his tongue worked Papyrus open he pulled out his aching cock with his free hand. Slim formed a tight ring of magic to fit over the base of his cock, knowing that he wouldn’t last one minute in Papyrus’s soft walls without it. It was painful since he was already so aroused, but that mix of pain and pleasure was making his head spin.

He couldn’t wait any longer, it was time to take what was his. 

Slim could have spent the whole day servicing that sweet pussy, but Papyrus was wet and ready from his previous climax. He made sure to pull away slowly, and not before teasing Papyrus’s clit with his tongue to make him lose his already shaky balance. Papyrus was easily moved back into his lap, facing him this time because there was no way in hell that Slim was going to miss and of his reactions. 

“have you done this before?” Slim lined himself up, teasing the head of his cock across Papyrus’s folds. He knew the answer, but he wanted to hear Papyrus confirm that he was his first. 

“N-no” Papyrus replied in a soft voice that made Slim’s chest rumble before he looked into Slim’s eyes with an expression full of wonder. “But You’re My Friend...You’ll Teach Me, Right?”

 _oh fuccck_. Papyrus really was perfect. Slim ran one of his hands up the side of Papyrus’s skull soothingly while his other hand wrapped around Papyrus’s spine. “i will, i’m gonna take real good care of you little pappy.”

Slim pulled Papyrus down onto his cock hard until he bottomed out, silencing his cries and flailing limbs with a kiss. Even though it was obvious Papyrus was surprised at the pain, his innocence didn’t extend to not knowing what a kiss was. For all Slim knew Papyrus probably thought this was romantic with the way he wrapped his arms around his shoulders and let Slim push his tongue inside. He let Papyrus get used to the feeling of Slim’s cock in his virgin passage while he indulged in their first kiss. Slim was never usually one for this kind of affection, but with Papyrus it just felt so fucking _good_.

He couldn’t be patient forever though; he used the leverage he had with his hand on Papyrus’s spine to start moving him up and down on his cock, meeting every slam down with a roll of his hips. Papyrus was all flailing limbs at first as he tried to comprehend what was happening, but the more he got used to it the more he actually tried to rock himself to Slim’s rhythm. Papyrus’s next climax came just as quickly, only this time his angel wasn’t as quiet. By the third time he came on Slim’s cock he was screaming, his voice ringing around Slim’s skull and imprinting on his memory. But when Papyrus was coming down from the high Slim noticed he was squirming even more than before. Granted Slim was rolling his over-sensitive clit between his fingers, but Papyrus’s mortified expression told him there was something else going on. 

“what’s wrong is this getting too much for you?” He teased with a smirk, pressing his thumb flat against the bundle of nerves. “you’re doing so well though, baby. i think you can take a little more”

“n-no it’s g-good i-i just…” _oh?_ all of Slim’s attention was pulled as Papyrus buried his face in his hands before mumbling his confession. “i-i need to go to the bathroom”

If he didn’t have his makeshift cockring on, Slim would have cum instantly. It was like all his giftmasses had come at once, the soda’s they had been drinking had finally caught up with his angel at the best time. It wasn’t often that he got to indulge in this particular kink of his, but Papyrus really was perfect monster to do it with. He looked so embarrassed, and with the way his body was shaking Slim could tell he was extremely close to losing control and humiliating himself. Slim’s cock pulsed as it sought release inside Papyrus’s soft magic, but there was no way he was gonna let himself cum and miss _this_.

“i find that kinda stuff really hot you know-” He leaned forward, pulling Papyrus’s hands away from his face. “-don’t worry about that little pappy, just let it happen.” 

Slim brought him into a kiss again, silencing any other protests while making Papyrus feel how much he wanted this. Slim continued to thrust upwards into him at a steady pace while Papyrus started to lose the fight with his control and whine into his mouth. It started as a few hot spurts of magic, but when Slim moaned and fucked him faster Papyrus lost control completely. The torrent of liquid magic covered them both in seconds and Slim could feel Papyrus’s tears falling down onto his face. But he could tell Papyrus felt good, the relief of letting go quickly making his pussy start to pulse and soon Slim couldn’t tell if his shaking was from pissing himself or the start of another orgasm. 

It was over far too soon, Papyrus’s stream dying down as he sobbed in a mix of embarrassment and relief. Slim wanted more, and a wicked idea made him wonder just how far he could push this. 

“hey don’t feel bad, that felt really good. but-”He picked Papyrus up, flipping him onto the floor on his hands and knees and before dispelling the magic ring around his cock. “how about i do it too? you that way i can show you just how _good_ ” 

With the amount of soda he had also consumed it only took a few seconds for Slim to be able to coax his magic forward. He aimed his stream at Papyrus’s quivering folds for a few moments before sinking back inside and keeping his stream steady. He feel the mix of embarrassment and arousal coming off his angel as he tried to get to grips with what was happening. Slim knew that this was something his double would never forget, and some primal instinct recognised this as a way of marking Papyrus as _his._ He could tell that Papyrus was enjoying it too; he was rocking back onto his cock, no doubt enjoying the change of angle and feeling of hot magic flooding him. And luckily for Papyrus, he got to be filled up twice.

As soon as Slim stopped pissing he was pounding into Papyrus again, moaning and growling as he let go of the last shreds of control. The sound of their wet magic meeting and the strong smell of sex and fluids was driving him crazy. He was so close, and he could tell Papyrus was too. Slim couldn’t help himself, he started babbling, wanting nothing more than to cum to the sound of Papyrus calling out for him. 

“fuck, pappy. you feel so good, are you gonna cum again? tell me what-”

“Y-Yes! I Love It! I-I’m Close- I W-Want To Feel You C-Cum Too! Please!”

 _fucking hell_. It was just what he needed to hear. Slim couldn’t control the growl that ripped from his throat as his thrusts became hard and uncoordinated. He chased his release in Papyrus’s pussy letting himself be milked when Papyrus clamped down around him again. As soon as he was done he pulled out, pushing Papyrus forward slightly to inspect just how wreaked he really was. Slim could see his cunt still clenching with aftershocks, going from tight to gaping wide open as their mixed magic dripped out of his pussy. Tears were still falling down his face as he whimpered happily and Slim hoped that the image burned into his mind. He never wanted to forget just how destroyed Papyrus was in this moment. 

Usually he was the type to fuck and leave, but his angel deserved so much better. Slim sat with his back pressed against the couch and pulled Papyrus into a hug from behind. Even though he had shattered all the boundaries between them, and they really needed to clean up before anyone came back, he wanted Papyrus to know straight away that he could look after him too. Slim showered him with kisses as he whispered praise against his skull, only pulling back when it looked like Papyrus had something to say. 

“what is it pappy? you can tell me anything” he said, tilting Papyrus’s skull so that he could see his face. 

“I-Um. I Really Enjoyed That, Thank You” Papyrus confessed with a giggle, moving forward to press his teeth against Slim’s. The kiss was chaste and sweet, but Papyrus’s dreamy expression afterwards made Slim’s soul hammer in his chest. 

He could tell there was more Papyrus wanted to say so he waited patiently. Still nothing could have prepared him for what his not-so-innocent angel said next. 

“Did You Want- Um. Would You Like To Do It Again?”


End file.
